Ed Miliband is considering demands by MPs for the judge in charge of the phone-hacking inquiry to be removed from his post after reports that he had socialised with members of Rupert Murdoch's family.
Sources close to the Labour leader said he shared the concerns raised over the impartiality of Lord Justice Leveson after it emerged that the judge attended two parties at the London home of Elisabeth Murdoch, the News Corporation chairman's daughter who is regarded as the heir to the business, and her husband, Matthew Freud.
David Cameron knew about the parties before appointing Lord Leveson to chair the inquiry into the scandal, Downing Street admitted.
In a separate development, it emerged that James Murdoch, the tycoon's son, could be recalled within days to the select committee investigating the scandal over allegations that he gave them misleading evidence. The Culture, Media and Sport committee may also call former News of the World editor Colin Myler and former NI legal manager Tom Crone over their claim that James Murdoch had been "mistaken" when he said that he had not seen an email suggesting the hacking scandal went further than just one rogue reporter.
One of the alleged hacking victims may include one of Britain's most senior policemen, who died from exposure while in turmoil over his private life.
Michael Todd, the Chief Constable of Greater Manchester Police, feared that a string of affairs was about to be made public by a Sunday newspaper, when he died while walking on Mount Snowdon in March 2008.
It is believed that his lover at the time of his death, Angie Robinson, had her phone hacked by journalists. It is not known whether those journalists worked for the NOTW. However, it has emerged that another woman romantically linked to Mr Todd, Andrea Perry, who at the time was reporting for the NOTW, is to be interviewed by detectives investigating hacking.
An inquest into Mr Todd's death said he had not committed suicide, but in the hours before his death he sent tortured text messages to women with whom he had been involved. A report into Mr Todd's conduct by Sir Paul Scott-Lee, Chief Constable of West Midlands Police, concluded his affairs made him vulnerable to blackmail.
Coincidentally, Sir Paul is now on Lord Leveson's inquiry panel.
Lord Leveson attended two parties at the London home of Mr Freud and Ms Murdoch, on 29 July last year and on 25 January this year.
A source close to the Labour leader said: "The Prime Minister must make clear whether he considered all aspects of the appointment [of Lord Leveson] properly. Ed is aware of and shares the concern about this."
A number of top executives at News International were told that the News of the World was breaking the law four years before the company finally abandoned its "rogue reporter" defence of illegal phone-hacking this year, The IoS has learned. They were warned that the newspaper had illegally obtained the medical records of Manchester United's manager, Sir Alex Ferguson, in 1997, when Phil Hall was editor and Rebekah Brooks his deputy.
The revelations are from a private and confidential statement, presented to executives by sports reporter Matt Driscoll at a meeting to discuss his appeal against dismissal in July 2007. Mr Driscoll, who was subsequently awarded £792,736 by an industrial tribunal, stated that he had "witnessed, first-hand, the kind of journalistic practice the News of the World would stoop to in order to get a story", after he had failed to substantiate rumours about Sir Alex's health.
It has also emerged that a Surrey police officer was taken off the hunt for the killer of Milly Dowler, whose phone was hacked by the NOTW, after leaking confidential details of the investigation.
An officer with knowledge of sensitive information was given "words of advice" and removed from the case after a complaint that he mishandled confidential data.
Surrey Police said it had no evidence that the officer had passed any information to the NOTW. But Labour MP Chris Bryant said: "This raises major questions about the original investigation and about the News of the World's relationship with other police forces. The problem is the Surrey police knew about this in 2002 and did nothing."